CVE-2021-38503

moderate-risk

Published 2021-12-08

The iframe sandbox rules were not correctly applied to XSLT stylesheets, allowing an iframe to bypass restrictions such as executing scripts or navigating the top-level frame. This vulnerability affects Firefox < 94, Thunderbird < 91.3, and Firefox ESR < 91.3.

Do I need to act?

1.1% chance of exploitation in next 30 days

EPSS score — moderate exploit probability

Not on CISA KEV list

No confirmed active exploitation reported to CISA

Patch status unknown

Check vendor advisories for fix availability and mitigation guidance

CVSS 10.0/10 Critical

NETWORK / LOW complexity

Affected Products (6)

Firefox

Firefox Esr

Thunderbird

Debian Linux

Affected Vendors

Debian Mozilla

References (20)

Issue Tracking https://bugzilla.mozilla.org/show_bug.cgi?id=1729517

Mailing List https://lists.debian.org/debian-lts-announce/2021/12/msg00030.html

Mailing List https://lists.debian.org/debian-lts-announce/2022/01/msg00001.html

Third Party Advisory https://security.gentoo.org/glsa/202202-03

Third Party Advisory https://security.gentoo.org/glsa/202208-14

Third Party Advisory https://www.debian.org/security/2021/dsa-5026

Third Party Advisory https://www.debian.org/security/2022/dsa-5034

Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-48/

Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-49/

Vendor Advisory https://www.mozilla.org/security/advisories/mfsa2021-50/